Due to fire and health hazards, the potential loss of produced fluids, and potential damage to the environment, there has been increased emphasis on use of downhole safety shut-off valves, e.g. storm chokes, for flowing petroleum wells. By means of a storm choke, the flow of petroleum fluids through the production tubing of a flowing well can be shut off in an emergency, thus providing means for preventing or controlling an accidental blowout.
Most of the storm chokes now used are of three basic types which are installed in the well bore:
1. A valve which automatically closes and thus shuts off flow of fluid when the pressure differential across the valve becomes too great. More specifically, a valve of this type is designed to shut automatically if the flow of fluid through it exceeds a certain limit.
2. A hydraulically activated valve to which hydraulic fluid is pumped from the surface when an emergency arises.
3. A valve through which the fluid will flow only if the pressure in the well bore at the valve is above a pressure at which the valve is preset to close and which closes automatically if the pressure falls below the preset value.
None of the valve arrangements mentioned above has proven to be altogether satisfactory because of total dependence upon fully automatic operating systems which sometimes fail or else because it has not always been possible to complete an action at the surface which is necessary for opening or closing the valve.
It is therefore an object of the present invention to provide a simple and reliable storm choke which can be secured in a normally open or closed condition and which will close or open automatically upon manual or accidental release of the securing means. Other objects and advantages of the invention will become apparent from the following description which is, of course, intended to be illustrative rather than limitative.